[PATCH] selinux: improve performance of sel_write_load()

[PATCH] selinux: improve performance of sel_write_load()

[zhanglin]

remove unecessary multiplications of sel_write_load().

Signed-off-by: zhanglin <zhang.lin16@zte.com.cn>
---
 security/selinux/selinuxfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index f3a5a138a096..4b2d87b6fcf9 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -117,6 +117,7 @@ static void selinux_fs_info_free(struct super_block *sb)
 #define SEL_CLASS_INO_OFFSET		0x04000000
 #define SEL_POLICYCAP_INO_OFFSET	0x08000000
 #define SEL_INO_MASK			0x00ffffff
+#define SEL_LOAD_MAX			0x04000000
 
 #define TMPBUFLEN	12
 static ssize_t sel_read_enforce(struct file *filp, char __user *buf,
@@ -550,7 +551,7 @@ static ssize_t sel_write_load(struct file *file, const char __user *buf,
 		goto out;
 
 	length = -EFBIG;
-	if (count > 64 * 1024 * 1024)
+	if (count > SEL_LOAD_MAX)
 		goto out;
 
 	length = -ENOMEM;
-- 
2.17.1

Re: [PATCH] selinux: improve performance of sel_write_load()

[Stephen Smalley]

On 9/17/19 3:20 AM, zhanglin wrote:
> remove unecessary multiplications of sel_write_load().

I'm not sure it is really a performance improvement since the compiler 
generates the same code (at least on x86_64).  I'm wondering though 
whether we still need this check at all.  It was originally patterned 
after a similar check for loading kernel modules, which was removed in 
f946eeb9313ff147075 ("module: Remove module size limit").

> 
> Signed-off-by: zhanglin <zhang.lin16@zte.com.cn>
> ---
>   security/selinux/selinuxfs.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index f3a5a138a096..4b2d87b6fcf9 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -117,6 +117,7 @@ static void selinux_fs_info_free(struct super_block *sb)
>   #define SEL_CLASS_INO_OFFSET		0x04000000
>   #define SEL_POLICYCAP_INO_OFFSET	0x08000000
>   #define SEL_INO_MASK			0x00ffffff
> +#define SEL_LOAD_MAX			0x04000000
>   
>   #define TMPBUFLEN	12
>   static ssize_t sel_read_enforce(struct file *filp, char __user *buf,
> @@ -550,7 +551,7 @@ static ssize_t sel_write_load(struct file *file, const char __user *buf,
>   		goto out;
>   
>   	length = -EFBIG;
> -	if (count > 64 * 1024 * 1024)
> +	if (count > SEL_LOAD_MAX)
>   		goto out;
>   
>   	length = -ENOMEM;
>